1. Field of the Invention
The present invention relates to a latch device for a vehicle tailgate having two doors, that is, a main door and a sub door.
2. Description of the Related Art
In the case of a tailgate having a main door and a sub door, from the viewpoint of the counter measure of safety and the prevention of damage of doors, there are some cases where the door-opening operation of the main door and/or the door-opening operation of the sub door may have some restrictions, and for example, in some cases, it is set that the door-opening operation of the main door is invalid when the sub door is in the open state.
U.S. Pat. No. 6,017,067 shows a typical tailgate latch device which has a main latch unit for keeping a main door in the closed state in cooperation with a main striker and a sub latch unit for keeping a sub door in the closed state in cooperation with a sub striker. A sub ratchet of the sub latch unit is connected to a clutch mechanism which is operatively provided between a main open handle and a main ratchet of the main latch unit. The clutch mechanism disconnects the main open handle from the main ratchet when the sub ratchet releases the sub latch of the sub latch unit.
The problem of the conventional latch device is in the point that the clutch mechanism is switched between the connected state and the unconnected state by the movement of the sub ratchet. The sub ratchet moves to be engaged with the sub latch by the elasticity of a ratchet spring, and it moves to be separated from the sub latch by the door-opening operation force of the sub open handle. The ratchet spring should have a comparatively strong elasticity so that it can make the sub ratchet engage with the sub latch instantaneously in response to the door-closing of the sub door. Additionally, it is necessary for the ratchet spring to have a force for moving plural parts of the clutch mechanism when moving the sub ratchet toward the sub latch, and therefore, the elasticity of the ratchet spring is set to be stronger. Such a strong ratchet spring hurts the good operational feeling of the sub open handle.
Accordingly, it is an object of the present invention to provide a latch device for a vehicle tailgate, wherein the above described problem is overcome by detecting the opening state of the sub door on the basis of the rotational position of the sub latch of the sub latch unit.
Furthermore, it is another object of the present invention to provide a latch device for a vehicle tailgate, wherein the sub door can be closed with no problem even when the door-opening operation of the main door is proceeding.